A Bayesian Kepler periodogram detects a second planet in HD 208487 |
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Authors: | P C Gregory † |
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Institution: | Physics and Astronomy Department, University of British Columbia, 6224 Agricultural Rd., Vancouver, British Columbia V6T 1Z1, Canada |
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Abstract: | An automatic Bayesian Kepler periodogram has been developed for identifying and characterizing multiple planetary orbits in precision radial velocity data. The periodogram is powered by a parallel tempering Markov chain Monte Carlo (MCMC) algorithm which is capable of efficiently exploring a multiplanet model parameter space. The periodogram employs an alternative method for converting the time of an observation to true anomaly that enables it to handle much larger data sets without a significant increase in computation time. Improvements in the periodogram and further tests using data from HD 208487 have resulted in the detection of a second planet with a period of 90982?92 d, an eccentricity of 0.370.26?0.20, a semimajor axis of 1.870.13?0.14 au and an M sin i = 0.45+0.11?0.13 M J. The revised parameters of the first planet are period = 129.8 ± 0.4 d, eccentricity = 0.20 ± 0.09, semimajor axis = 0.51 ± 0.02 au and M sin i = 0.41 ± 0.05 M J. Particular attention is paid to several methods for calculating the model marginal likelihood which is used to compare the probabilities of models with different numbers of planets. |
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Keywords: | methods: numerical methods: statistical techniques: radial velocities stars: individual: HD 208487 stars: planetary systems |
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